Radiant heating tube



y 193& H. H. HARRIS 2,115,769

RADIANT HEATING TUBE Filed Aug. 22, 1936 INVENTOR His/:BY H. HARRs ATTORNEYS Patented May 3, 1938 UNITED STATES V 2,ll5,769'

PATEN'T. OFFICE 7 Claims.

This invention relates to 'radiant heating tubes, particularly for annealing i'urnaces.

It is an object of this invention to provide a radiant heating tube, particularly for use in annealing furnaces, which will give a greater heat i liberation for a given heat input and atgiven length of tube.

It is a further object to provide a tube which will give more thorough combustion of the fuel as it passes through the tube.

A further object is to provide a tube which will give a more uniform heat liberation throughout its length.

Further objects will become apparent during the course of the specification. r

In the drawing,

Fig. 1 is a vertical sectional view of a tube in accordance with my invention', showing same in association with a portion of the housing and flttings of an annealing furnace;

Fig. 2 is a horizontal section taken on the line 2--2 of Fig. 1;

Fig. 3 is a side elevation, partially in section, of a second form of my invention;

Fig. 4 is a horizontal section on the line 4-4 of Fig. 3;` and Fig. 5 is a side elevation, partiaily in section, of a third form of my invention.

Radiant heating tubes such as hereln disclosed are generally arranged in two rows along opposite walls' of a furnace chamber. As such furnaces are well known, I have not shown the complete assembly, but have indicated enough to` aflord an understanding o! my invention.

Having particular reference to Figs. 1 and 2, reference character o designates an insulation wall of the iumace, with an outer cover plate i2.

An inner heat conductive plate i4 is preferably interposed between the tube chamber I! and the dharge s on the platform or other support 20.

A manifold 22, carried on supports 24, 26, supplies mixed fuel to any desired number of combustion jets 28 controlled by valves 29. Each burner jet extends into a heating tube'30, whose end is sealed' as by a cap 32 about the jet. These heating tubes are preferably cast, and made oi' a high heat resisting alloy.

Each heating tube is tor-med with a longitudinal tubular central portion 34 and transverse tubular end portions 36, 38. These end portions extend out through the insulation wall lo and cover plate l2, disposing the main central portion 34 of the tube vertically between the wall o and the'heat conductive plate l4.

Where the upper end portion 30 extends ou through the wall n an elbow or other fltting 40 secures an exhaust pipe 42 thereto. and an insulated cover box 44 'surrounds the jointsand the opening through the wall.

` Each heating tube 30 is shaped to' cause. the burning gases to swirl as they pass therethrough. In the form of Figs.l and 2, 'the longitudinai central portion 34 of the tube is formed with spiral corrugations 35, which correspond on the interior and exterior, the thicknessoi the walls being substantially uniform throughout, and the elbow bend 31 between the central portion 34 and the lower transverse portion 38 is preferably ofiset as shown at 31, Fig; 2. This ofiset is to the side which will start the gases rotating in the same direction as the spiral grooves in the longitudinal central portion.

Thus when the burning gases from the jet 23 reach the bend 31 ,they are diverted upwardly, as seen in Fig. 1, and also 'diverted to the left, as

li u

seen in Fig. 2. This imparts to them an initiai rotation which is continued not only by momentum but also by the spiral grooves.

Thus the burning gases are whirled and eddied, whereby combustion is more complete endemcient. Moreover, the burning gases are thrown into more intimate contact with the walls of the radiant heating tube, both because of centrii'ugal force and because of the longer path which they traverse in following the spiral. The tube also has a greater surface exposed to the gases because of its spirally corrugated form, and likewise a greater outside surface for radiating heat. Thus with my invention there is improvement in the combustion of the gases, in the transfer of their heat to the tube, and in the radiating of heat by the tube.

In Figs. 3 and 4 I have shown a modified form of heating tube in accordance with my invention, in which the longitudinal central portion 344 of the tube is provided with sp'iral corrugations "a, and the bend 3'Ia between the central portion a, and the bottom transverse portion :la is not offset but is provided with continua. tions of the spiral corrugations, so that the bum ing gases impinge upon the beginnings of the spirai corrugations as they issue from the jet.

In these figures I have also shown another feature which may be used with any o! the forms of tube in accordance with my invention. 5. `preiferably solid core 46 is positioned axially the central portion 340. of the tube. The outer surface of this core is provided with corrugations 41 which spiral' in the opposite direction from those of the tube itself. As a result the gases rotate in the direction of the spirals in the tube as they pass `up through the tube, while the opposite spirals onthe core partially break up and reverse the swiri of the gases, creating a turbulence which more thoroughly mixes the gases and causes them to eddy. There-by all the particles of 'the gases are assured of repeated contact with the surface of the heating tube, whereby the heat of the gases is more thoroughly transferred to the tube for radiation thereby.

In Fig. I have shown a third modification, having spital corrugations 351 which start below the bend 'lb and continue throughout the central portion b, in which the diameter oi' the tube is reduced progressively from the bottom of central portion Mb to the top thereof. As a result, the proportion of surface area to enclosed Volume is increased, and the speed of flow of the gases is also increased. The gases cool off toward the top, having given off some'of their heat at the lower part of the tube. These cooler gases are with this tapered tube sent through faster and in contact with surface area which is greater in proportion to the thickness of the stream of gases. Thus these cooler gases are caused to give ofl their heat more rapidly, and the upper part of the heating tube is as hot as the lower part, thereby giving uniform heating.

It will be understood, of course, that variations and changes may be made within the 'scope of my invention, and the several features may be used independently or in various combinations, as tor example, the core shown in Fig. 3 may beused with the forms of tubes shown in either Figs. 1 and 2 or Fig. 5, as well as with the form of tube shown in Figs. 3 and 4.

I claim:

1. A heating tube having a principal longitudinal portion provided with interier spiral corrugations, and having a transversely extending entrance end portion provided with oblique deflecti ing means angled in the same rotationai direction as the spiral corrugations of the principal longitudinai portion.

2. A heating tube having a principal longitudinal portion provided with interior spirai corrugations,` and having a transversely extending entrance end portion, said end portion having oblique deflecting means, and said interier spiral con'ugations extending around the bend between the principal portion and the end portion.

3. A heating tube having a principal longitudinal portion provided with interior oblique deflecting means, and having a transverseiy extending entrance end portion, said end portion being offsetwith respect to said principal portion to the side which imparts to entering gases a spiral rotation in the same direction as the oblique deflecting means in the principal 'iongitudinal portion.

- 4. A heating tube 'comprising a principal longitudinally extending portion having interior spiral corrugations and having an outiet, a transverse tubular entrance member, a burner jet therein, and an oflset elbow connection between the transverse and elongated tubes, the ofl'set and the spiralcorrugations being arrangedto cause gases traveliing through to swirl in the same rtative sense.

5. A heating tube having spiral corrugations in its in'ner surface and a core within said tube. said corehaving spiral corrugations on its outer surface, the'spiral corrugations on said core running in the reverse direction from. those in the tube.

6. A heating tube having longitudinal 'spirai corrugations and having an entrance end, said tube decreasing gradually in diameter as ,it extends farther away 'from its entrance end.

7. In a heat treating furnace, a radiant 'heating tube having a principal longitudinal portion, oblique deflecting means within said portion, a transverse entrance end portion, a -burner-nozzle within said end portion for directing burning gases to impinge upon the bend between said end portion and said longitudinal portion, and oblique deflectingmeans at the said bend upon which said gases impinge. said deiiecting means at the bend imparting rotation in the same rotational direction as said deflecting means in the longitudinal portion.

HENRY H. HARRIS. 

